Portable dimpler



May 28, 1963 H. A. SCHMITT PORTABLE DIMPLER llY INVENToR. H uff/er A. .SWW/rr A 7 rae/V675 United States Patent O Delaware Filed Oct. 24, 1960, Ser. No. 64,397

8 Claims. (Cl. 153-21) Dimpling operations are effected in sheet metal workpieces, particularly in aircraft manufacture, in order that tapered head rivets may maintain their outer head surface flush with the surface of the skin through which they pass. The only portable tool heretofore 'available and known to me for the purpose incorporates a C-trame which supports .a die at the end of one arm of the C, and at the opposite arm of the C a punch is movable towards the die, to eiiect the dimpling operation. -Not only is -such a C-yoke dimpler heavy, for it is subjected to heavy loads, but its use is limited by the depth of the throat of the C-trame, which must be relatively small because ofthe load to which it is subjected. It, 'for example, this depth is no greater than six inches, a dimple cannot be formed with it at a greater distance from the edge of the sheet. It not infrequently happens that dimples must be lformed at a greater distance. lIn consequence of the limitation imposed by the C-rame dimpler the work can not be done by a portable tool, and the only way known of dimpling the work is to remove the sheet from its installed position, and to carry it to and dimple it at a fixed dimpler. This runs the risk of damaging a workpiece on which many man-hours have been expended, besides the labor of removing and reinstalling it.

This invention concerns a portable dimpler which is capable of forming dimples in a workpiece without limitation as to distance from an edge, with great accuracy, and without imposing Iloads on the mechanism beyond limits that it can easily withstand, nor requiring the operator to handle heavy tools. In particular the tool of this invention enables greater flexibility of design and planning in the work, reduced cost for modiiication and repair work, and increased production versatility, yet `all within a tool that need weigh no more than six pounds, and which can be used for cold dim-pling or for hot dimpling. The tool is adapted to form dimples of various sizes in relation to holes of varying diameters, land it can be operable by hydraulic Ipower or the like.

Details of the invention will be better understood from a study of the accompanying drawing wherein the invention is shown in a presently preferred form, and from this specication, and the novel features of the invention, will be set `forth in the accompanying claims.

FIGURE l is an axial sectional view through the separated elements of such a portable dimpler ready for installation to effect a dimpling operation.

FIGURE 2 is a view similar to FIGURE l but showing the dimpler installed in relation to a workpiece, and FIGURE 3 is a similar view but showing the dimpling accomplished.

FIGURE 4 is a side elevational View of an end of the die portion of the dimpler, and FIGURE 5 is in part an end view .and in part a section illustrating the same portion of the mechanism.

The heart of the tool is a mandrel 1, preferably made of high strength tool steel. Vascojet 1000, a tool steel of the SAE I-I-ll series, has been used for tools now in use. It has high tensile strength, which is an essential characteristic. This mandrel is formed at one end with threads 10. These threads are preferably shallow, so that they reduce the eective diameter oi the mandrel at the point of application of tensional forces by the smallest amount, and it is desirable that the reduction be the minimum prac- Mice tical, to maintain the tensile strength of the mandrel at a maximum. At its opposite end the mandrel is threaded or otherwise formed, as indicated at 11, -for securement to an actuator. The threads 111 may be of larger diameter than the etiective diameter of the mandrel, for only the end that carries the threads 10 must tit -within a hole in a workpiece W, about which hole a dimple is to be formed. The mandrel should lit rather snugly in the hole, and it will be desirable to provide diierent sizes of mandrels for holes of different diameter.

Without at this time going into the structure of the mechanism for actuating the mandrel and associated elements it may be pointed out here that a pressure pad 2 surrounds the mandrel at its end ydistant from the threads 10, and serves as a stop against which the workpiece may be pressed. Also, a punch 3 surrounds the mandrel at the same end and reciprocate/s within the iixed pressure pad 2, or the housing 7 on which the pressure pad is mounted.

A die d which cooperates with the pressure pad 2 and punch 3 is, in use, atlixed to the threaded end 10 of the mandrel, but must be quickly mountable thereon and dismountable therefrom, and when mounted must be securely held against relative movement even under the heavy forces prevalent during operation. The die 4 is threadedly engaged at 40 with a collar 41 so that in effect the die 4 and collar 41 become component parts of a single element. A split nut, indicated in general by the numeral 5, is threaded at 50 complementally to the threads 1). This nut is made up of a plurality of longitudinal `segments 51 which together surround the mandrel 1 and its threaded portion 10. For quick engagement and disengagement the segments 51 are separable and contractible. The several segments are surrounded by a contractile ring such as the rubber ring 52, and their ends are chamfered as at 53, whereby the contractile ring 52 tends to spread them at their threaded ends. At the latter end they are externally of conical shape, as indicated at 54, and when urged into the collar 41, which is complementally conically recessed at 42, the segments are closed down tightly upon the threads 10. To etect engagement of the threads S0 with the threads 10 it is only necessary to move the nut 5 in the axial direction onto the threaded end of the mandrel 1, its threaded ends being then spread apart so that the nut will slip over the shallow threads l1l). Once the nut 5 is in position it need only be pressed in the axial direction toward the small end of the conical recess 42, and rotated slightly, which closes down the segments 551 upon the threads 10 of the mandrel, and in a very short movement squeezes the nut so tightly upon the mandrel that despite the shallowness of the threads 1t) and 5t? they will resist the forces to which the mandrel is subjected.

Since it is inconvenient to handle the nut 5 and its segments 51 as a separate assembly, it is conveniently surrounded by the hood 6 connected by pins 55 with each segment 51 in such manner that the segments have freedom of individual movement relative to the hood, and the hood is mounted on the collar 41 in such manner that it will not separate therefrom. For example, pivot pins 44 in the collar 41 project through axially directed slots 60 in the hood, and a spring 61 reacting between the interior of the hood and the end face of the collar 41 urges the hood to its outermost position, in which the segments 51 are spread apart. A camming locking lever 62 pivoted upon the pivot pins 44 and so upon the collar 41, is provided with a cam or hook 64 (see particularly FIGURE 4) to engage pins 63 outstanding from the hood 6, and when engaged therewith, as in the full line position of FIGURE 4, maintaining the spring 61 compressed and urging the segments 51 into the conical recess 42. When the locking lever 62. is moved to the dot-dash line position of FIGURE 4 the spring 61 urges the hood 6 to its outermost position,

wherein the segments 51 of the nut are easily disengaged from the mandrel and separated.

Two independently operable motor means are required to complete the tool, one for drawing the mandrel 1 with the die secure-ly aiixed to it towards the fixed pressure pad 2, to clamp the workpiece W between them, as in FIG- URE 2, and the other motor means active thereafter to urge the punch 3 towards the workpiece and the die 4, to form the dimple. It will be understood, of course, that the ydie is shaped at 49 to form one surface of a dimple, and the punch -3 is complementally formed at 39 to form the opposite face of the dimple. FIGURE 3 shows the dimpling operation completed. p

The motor means thus required may be incorporated within a housing 7 having two cylinders 71 and 72. Within the Vcylinder 71 is a clamping piston 73 which has an axial extension 74, internally threaded to receive the threads 11 of the mandrel. It also has an extension 70 projecting eXteriorly of the cylinder 71 and squared or otherwise formed for reception of a wrench, so that the connection of the mandrel with the threads 11 can be effected. Springs 75 urge the piston 73 in the one direction, as is best seen in FIGURE l. In the bore 72 a ram or piston 76 is reciprocable, this having an extension 76a which contacts the end of the punch 3 to move the latter in the downward direction as viewed in FIGURE l. Springs 77 return the piston 76 when the motive force is removed. Y

Motive force is supplied preferably from a hydraulic source entering at 8 past a suitable valve means, such as the spring-closed valve S1, to the passage 78 and thence to the cylinder 71 to urge the piston 73 in the direction in opposition to the springs 75. The effect of this is to draw the mandrel 1 upwardly, as viewed in FIGURE 1,V and with it the die '4, until the workpiece W is clamped .between the pressure pad 2 and the die 4. The pressure .is exerted about an annular area spaced outwardly from and surrounding the mandrel 1. Next the motive fluid is admitted past a spring-closed valve 82v and into a passage 79 which communicates with the interior of the cylinder 72, acting to urge the piston 76 in the downward direction, which causes the punch 3 to move toward the die 4 and in cooperation therewith to form the dimple as in FIGURE V3. Actuation of the valves 81, 82 may be accomplished by suitable means such as the lever 80.

It is preferred that there be a ram 9 within the aperture 49 of the die 4, this being urged outwardly of the depression 49 by spring means 90. 'Ihis ram will yield under the force of the punch 3 but will assist in forming correctly the interior of the dimple. VThe force of the spring 90 may'be adjusted as desired by threading of the collar 41 within the die 4, inwardly or outwardly.

It isbelieved that the operation will be self-evident. A mandrel, together with a punch 3 and pressure pad 2, of -appropriate size, is supported from the housing 7, the mandrel being threaded in at 11 tothe extension 74 of the piston 73. Various sizes can be employed, Vdue to the threaded connections. Now the end of the mandrel which is threaded at is passed through the hole in the workpiece about which a dimple is to be formed, and the die Y4 with its associated elements is slipped over the threads 10 vof the mandrel and the nut 5 is closed down on the threads, and Viixes the die securely in position upon this end of the mandrel, but at the opposite side of the workpiece from the housing 7 and associated parts. Now

the'valves 81 and 82 are opened in succession. Opening of the valve I81 urges the piston 73 upwardly as viewed in FIGURE 1, and draws the Vdie 4 against one face of the workpiece W, the opposite :face of the workpiece being pressed against the pressure pad 2 and the workpiece thus being clamped between these two elements. The immediately following opening of Vthe valve S2 urges the piston 76 and hence the punch 3 toward the workpiece and the complemental faces 39 and 49 of the punch and die, re-

spectively, form the dimple. The ram 9 moves inwardly but in so doing slightly coins the raised inner edge of the dimple. Immediately the trigger 8 is released, the valves reclose, and the cylinders 71 and 72 are vented, by means not shown, and the springs 75 and 77 return the pistons to their normal positions. It is now possible to throw the locking lever 62 to the unlocked position, shown in dotdash lines in FIGURE 4, to unscrew the nut 5 slightly, whereupon its segments will separate and it can be immediately withdrawn endwise from the mandrel, and the mandrel can be withdrawn from the hole in the workpiece.

It will be clear that a device such as this is operable without regard to what distance inward from an edge may be the hole which is to be dimpled. Furthermore, if hot vdimpling is desired the exterior of the pressure pad 2 may receive a surrounding heating element, shown in FIGURE 3 in dot-dash lines at H, by which means the punch will be maintained heated. If need be a similar heating element may surround the die 4.

Suitable pressure sealing devices and the like are shown, and would be provided as needed, bu-t being conventional they do not need specific reference here.

I claim as my invention:

l. Dimpler apparatus comprising a housing having a pressure resistant annular pad forming one end thereof, an annular punch disposed in the housing and freely slidable in the pressure resistant pad for movement relatively into and out of the housing, a clamping piston mounted coaXially with the punch for movement relatively toward and away from said end of the housing, a mandrel eX- tending through the punch and having one end portion thereof detachably engaged with the piston for Amovement therewith, a die detachably engaged with the mandrel to clamp a workpiece against the pressure resistant pad under the action of the piston, and punch actuator means operable to drive the punch relatively out of the housing into dimpling engagement with Vthe clamped workpiece.

2. Dimpler apparatus according to claim Y1 wherein the punch actuator means includes a member operable independently of the clamping piston to drive the punch ,relatively out of the housing for the dimpling process.

comprising independently operable motor means Vfor actuating the clamping and annular pistons.

5. Dimpler apparatusaccording to claim 3 wherein the clamping piston is mounted in the housing for reciprocal movement relative to said end thereof and the die is detachably engaged with the other end portion of the mandrel.

V6. Dimpler apparatus according to claim 5 wherein the clamping piston has an axial extension on one end with a socket therein in which the mandrel is detachably engaged and the annular piston is'slidably engaged about the axial extension of the clamping piston.

`.7. Dimpler apparatus according to claim l wherein the die includes a tubular die member the inner wall of one end portion of which tapers conically inwardly of the member, and a longitudinally segmented tubular member engaged in said end portion of the die member and having a complementally taperedV outer Vwall and a threaded inner wall, the other end portion of the mandrel being complementally threaded with and engaged in said segmented tubular member.

8. Dimpler apparatus according to claim 7 further comprising bracket means pivotally mounted on the tubular die member and having said segmented tubular member connected therewith for swinging movement into and out of said end portion of the die member.

(References on following page) References Cited in the le of this patent UNITED STATES PATENTS Fischer Nov. 2, 1943 Fischer July 11, 1944 5 Huck Dec. 2, 1947 6 Rees Feb. Z3, 1954 Wing et al. Apr. 23, 1957 

1. DIMPLER APPARATUS COMPRISING A HOUSING HAVING A PRESSURE RESISTANT ANNULAR PAD FORMING ONE END THEREOF, AN ANNULAR PUNCH DISPOSED IN THE HOUSING AND FREELY SLIDABLE IN THE PRESSURE RESISTANT PAD FOR MOVEMENT RELATIVELY INTO AND OUT OF THE HOUSING, A CLAMPING PISTON MOUNTED COAXIALLY WITH THE PUNCH FOR MOVEMENT RELATIVELY TOWARD AND AWAY FROM SAID END OF THE HOUSING, A MATERIAL EXTENDING THROUGH THE PUNCH AND HAVING ONE END PORTION THEREOF DETACHABLY ENGAGED WITH THE PISTON FOR MOVEMENT THEREWITH, A DIE DETACHABLY ENGAGED WITH THE MANDREL TO CLAMP A WORKPIECE AGAINST THE PRESSURE RESISTANT PAD UNDER THE ACTION OF THE PISTON, AND PUNCH ACTUATOR MEANS OPERABLE TO DRIVE THE PUNCH RELATIVELY OUT OF THE HOUSING INTO DIMPLING ENGAGEMENT WITH THE CLAMPED WORKPIECE. 